Theater Flats and Periaktoi

[Prashun Patel]

I've been asked by my kids' school to make a set of rotating, triangular prisms that can serve as scenery backdrops.

Has anyone had experience constructing these?

[Jamie Buxton]

No experience, but I'm intrigued. How big do they want? Too big to rotate on a standard lazy-susan bearing 12"? For bigger, you're probably into fixed casters, and iron pipe to form the pivot pin in the middle. For the prism itself, probably just plywood butt-glued at the corners.

If the prisms are scaled for a large stage, do you have a big truck to move them, and a big door at the show? Or are you going to need to do it KD-style -- carry in parts, and assemble them on site?

[Michael Weber]

Stage flats are generally built with 1x2 material with butted corners and 1/4 inch plywood triangle corner braces and covered with muslin. The muslin is glued around the parameter and when painted, becomes quite tight. Triangle braces go on the back of course and tall flats will need additional cross piece, again braced with plywood, to keep the side from bowing in when the muslin shrinks. I don't see any problem angling the vertical side pieces to attach three together. That would actually make it quite rigid and not need external support.
http://m.wikihow.com/Build-a-Theatre-Flat

[Prashun Patel]

This is what I need help with - I am not sure of all the features that would be beneficial to them. I need to make 8 that are 6ft high, and about 2' on a side.

I'll do them on casters; lazy susans and pivots will be a little pricey. Middle schoolers need to be able to roll them around.

The easiest construction would be to build half-lapped triangular rib cages that would be supported by a couple 2x4 spines through the center, and then 1/4" hardboard sheathed on the ribs.

However, this would not provide nailing surface for the sheaths along the edges. I don't know if the board will become wavy over time if I do it that way.

The other way is to bevel (3) 2x4 spines that form the corners, and then to pocketscrew horizontal 2x4's in between these.

[Charles Lent]

The 2X4's are going to get heavy. 1X2 or 1X3 will be lighter. If you can rip 2X4's into triangles for the corners it would work. Can you get away with using short pieces of these rather than full length continuous? Use 1/4" plywood for gussets at the corners (on the inside).
So the prisms pivot around a roughly central point, consider using non swivel casters placed properly so the prism can rotate around a central point without needing a central stationary pivot point. Make the frames strong but light. The muslin will shrink well and make the surface quite tight. I hope you have a big box truck to move them.

Charley

[Shawn Pixley]

Prashun,

I have built almost exactly what you described. Mine were a roughly 4'x4' platform on casters. On top of that was a lazy susan (for a CRT TV) and a second platform with indexing stops. On the rotatating platform was a prism shaped structure made from gatorboard (like foam core but with a fiberglas outer sheet). On each of the faces, there was a portion of the backdrop / scene. How can I help you?

[Tom M King]

I've built some triangular ones. You want them as light as possible. We just put casters under the corners. That way, during scene changes they can just be pivoted, and also easy to roll on and off stage. Simple is good on set stuff. I just used 2x2's and 1/4" plywood. They've been used on and off for over 20 years now.

[Prashun Patel]

Shawn-
Got any pix? Glad to see you here!!!

Thanks, Tom. I'd like these to last a long time too. Do you think pocket screwing the cross members to the uprights will be rigid enough for the long haul?

[Shawn Pixley]

Shawn-
Got any pix? Glad to see you here!!!

Thanks, Tom. I'd like these to last a long time too. Do you think pocket screwing the cross members to the uprights will be rigid enough for the long haul?

Prashun,

My general comment it that you are making the structure too heavy. If this is theater and indoors, light scrim type structures will work. Think 1x structure with a sized canvas scrim that can be painted on them. Think stage craft, not construction. With mine I used Gator board and hinged the three panels together and fastened with industrial velcro. The "prism" was then placed over 3 cleats in a triangular pattern over the rotating panel on top of the lazy susan. They were pinned to the cleats so that wind did not blow them over (Mine were for marching band outdoor performances). Yours should be easier.

Sorry, I have no Pix but I may be able to develop in Sketchup to illustrate after a medical app't this afternoon.

[Tom M King]

Our community theater is in an old school building, but the building is not used for anything else. All the old classrooms are used for shop, and storage. There was plenty of room, so no need for anything to break down. The "revolves" just got rolled out the door from backstage, down the hall, and into one of the storage rooms. If I'm remembering correctly, I just sewed the corners of the 2x2 frame together with 2-1/2" pneumatic finish nails. There was no framework other than around the edges.

Not nearly as complicated as my method of flying, and spinning Dorothy's house, or flying monkeys......pretty good at lightweight trees too.

I'm known there as Tom "the Lion" King, but that's been a long time ago.

[Prashun Patel]

Taking the advice to make them light, and for rigidity along the sides, I decided to make verticals out of ripped 2x4's.

The issue was how to allow a simple joint for the cross bracing.

These uprights are simple to make. You rip a bevel @ 30 degrees, then flip it and rip a second bevel, reset the blade to 90, and rip square sides to each of the exterior faces.

This allows the cross braces to all have square, butt faces (did I say that? ;)) I will make them out of 1x3 stock.

I cannot decide whether to Domino or Pocket screw them... I ruled out dowels, because the Jessem jig I have does not allow easy clamping to non-square faces. Pocket screws only require me to drill into the cross braces, which are squared joints. However, clamping the joint (when screwing) may get tricky since the verticals don't have a really good bearing surface for the clamp. Here's where a Domino excels: the locations of the joints are striked, and one side is drilled oversized, so the alignment isn't critical on the strike. But here's the magic: when the dominos are inserted, the eccentric verticals will stay true even when clamped. The dominos force the joint to be aligned. The other nice thing about the Dominos is that they won't interfere with any nails I use when tacking the sheathing in place...

Ok, so Domino it is...

[Prashun Patel]

The skeletons are done. I decided to use pocketscrews. They were much faster than dominos and required no glue dry time.

I'm using hardboard as the sheathing but got advice from a theater set designer that it was a bad choice because when it takes latex paint it becomes wavy. I am planning to use Zinsser BIN to prime it anyway. Let's see!